let a = "Tom";

let b = 'hello, I am ' + a + 'how are you'

let c = `hello, I am ${a} how are you`

let qq = '652501825@qq.co'
// console.log(c.includes('hello'));
// console.log(c.startsWith('he'));
// console.log(qq.endsWith('@qq.com'));



let num = 123
console.log(Number.isNaN(num));